The most common reason for algae to appear in a swimming pool is from improper pH and chlorine levels. The chemicals that are introduced into the swimming pool's filtration system are there to get rid of algae and other bacterial growths. Once the algae has appeared onto a vinyl pool liner it is not hard to get rid of, but it is a good indication it is time to check the pool's chemical levels. Once you have the algae removed, be sure to maintain the pool at its proper pH and chlorine levels to prevent the algae from coming back.
Things You'll Need
Soft nylon brush
Test kit (pH and chlorine)
Dry sodium bisulphate
Scrub the algae with a soft nylon brush. In most cases this is all that is needed with vinyl pool liners. If the stain is old or excessive then the pool may have to be shocked to remove the stain.
Check the pH levels of the pool with the test kit. Algae require a high pH level in order to thrive, so you should find that the pH levels are a bit high.
Don the safety glasses and rubber gloves.
Add dry sodium bisulphate to the pool to reduce he pH rating. Before shocking the pool you want the pH levels to be between 7.2 and 7.4. Use the swimming pool calculators resource below to find the correct amount of sodium bisulphate that your size pool requires. Apply the sodium bisulphate per the manufacturer's instructions.
Add four times the normal amount of chlorine for your pool. This procedure is called "shocking." It is best to do this during the night hours, because the ultraviolet rays of the sun can diminish the effectiveness of the chlorine.
Use the test kit to check the chlorine levels. The desired chlorine level is between 1 and 2 parts per million.
Use the soft nylon brush to scrub the remaining algae from the pool.
Use your pool vacuum to remove the algae debris during the cleaning process.
The filtration system should be on during all of the above procedures.
The swimming pool should be off limits during the cleaning process. When using the sodium bisulphate, read and abide by the safety instructions carefully.